The Company accounts for revenue in accordance with Topics 606 and 853. Topic 606 requires entities to recognize revenue when control of the promised goods or services is transferred to customers at an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those goods or services.

The Company accounts for a contract when it has the approval and commitment from both parties, the rights of the parties are identified, payment terms are identified, the contract has commercial substance and collectability of consideration is probable. Once a contract is identified, the Company evaluates whether the combined or single contract should be accounted for as more than one performance obligation. Substantially all of the Company's revenues come from the following two types of arrangements: Lease type and Management type contracts.

Under lease type arrangements, the Company pays the property owner a fixed base rent or payment, percentage rent or payment that is tied to the facility’s financial performance, or a combination of both. The Company operates the parking facility and is responsible for most operating expenses, but typically is not responsible for major maintenance, capital expenditures or real estate taxes. Performance obligations related to lease type contracts include parking for transient and monthly parkers. Revenue is recognized over time as the Company provides services. Certain expenses, primarily rental expense for the contractual arrangements that meet the definition of service concession arrangements, are recorded as a reduction of revenue for the three and six months ended June 30, 2020 and 2019, respectively.

Management type contract revenue consists of management fees, including both fixed and performance-based fees. In exchange for this consideration, the Company has a bundle of performance obligations that include services such as managing the facility as well as ancillary services such as accounting, equipment leasing, consulting, insurance and other value-added services. The Company believes that it can generally purchase required insurance for the facility and facility operations at lower rates than clients can obtain on their own because the Company is effectively self-insured for all liability, workers' compensation and health care claims by maintaining a large per-claim deductible. As a result, the Company generates operating income on the insurance provided under its management type contracts by focusing on risk management efforts and controlling losses. Management type contract revenues do not include gross customer collections at the managed locations as these revenues belong to the property owners rather than the Company. Management type contracts generally provide the Company with management fees regardless of the operating performance of the underlying facilities. Revenue is recognized over time as the Company provides services.

Service concession agreements within the scope of Topic 853 include both lease type and management type contracts. Revenue generated from service concession arrangements is accounted for under the guidance of Topics 606 and 853. Certain expenses (primarily rental expense) related to service concession arrangements and depreciation and amortization, have been recorded as a reduction of Service revenue - lease type contracts.

Contracts are often modified to account for changes in contract specifications and requirements. The Company considers contract modifications to exist when the modification either changes the consideration due to the Company or creates new performance obligations or changes the existing scope of the contract and related performance obligations. Most contract modifications are for services that are not distinct from the existing contract due to the fact that the Company is providing a bundle of performance obligations that are highly inter-related in the context of the contract, and are therefore accounted for as if they were part of that existing contract. Typically, modifications are accounted for prospectively as part of the existing contract.

Taxes assessed by a governmental authority that are both imposed on and concurrent with a specific revenue-producing transaction, which are collected by the Company from a customer, are excluded from revenue.

The Company recognizes both revenues and expenses, in equal amounts, that are directly reimbursed from the property owner for operating expenses incurred under a management type contract. The Company has determined it is the principal in these transactions, as the nature of its performance obligations is for the Company to provide the services on behalf of the customer. As the principal to these related transactions, the Company has control of the promised services before they are transferred to the customer.

The Company disaggregates its revenue from contracts with customers by type of arrangement for each of our reportable segments. The Company has concluded that such disaggregation of revenue best depicts the overall economic nature, timing and uncertainty of the Company's revenue and cash flows affected by the economic factors of the respective contractual arrangement. See Note 14. Business Unit Segment Information for further information on disaggregation of the Company's revenue by segment.

A performance obligation is a promise in a contract to transfer a distinct good or service to the customer or client, and is the unit of account under Topic 606. The contract transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. The majority of the Company's contracts have a single performance obligation that is not separately identifiable from other promises in the contract and therefore not distinct, comprising the promise to provide a bundle of monthly performance obligations or parking services for transient or monthly parkers.

The contract price is generally deemed to be the transaction price. Some management type contracts include performance incentives that are based on variable performance measures. These incentives are constrained at contract inception and recognized once the customer has confirmed that the Company has met the contractually agreed upon performance measures as defined in the contract.

The Company's performance obligations are primarily satisfied over time as the Company provides the related services. Typically, revenue is recognized over time on a straight-line basis as the Company satisfies the related performance obligation. There are certain management type contracts where revenue is recognized based on costs incurred to date plus a reasonable margin. The Company has concluded this is a faithful depiction of how control is transferred to the customer. Performance obligations satisfied at a point in time for the three and six months ended June 30, 2020 and 2019, respectively, were not significant.

The time between completion of the performance obligation and collection of cash is typically not more than 30 - 60 days. In certain contractual arrangements, such as monthly parker contracts, cash is typically collected in advance of the Company commencing its performance obligations under the contractual arrangement.

On June 30, 2020, the Company had $107.4 million related to performance obligations that were unsatisfied or partially unsatisfied for which the Company expects to recognize revenue. This amount excludes variable consideration primarily related to contracts where the Company and customer share the gross revenues or operating profit for the location and contracts where transaction prices include performance incentives that are constrained at contract inception. These performance incentives are based on measures that are ascertained exclusively by future performance and therefore cannot be estimated at contract inception by the Company. The Company applies the practical expedient that permits exclusion of information about the remaining performance obligations that have original expected durations of one year or less.

The Company expects to recognize the remaining performance obligations as revenue in future periods as follows:

(millions) (unaudited)	Remaining Performance Obligations
2020	$	24.0
2021		35.8
2022		20.4
2023		13.0
2024		7.2
2025 and thereafter		7.0
Total	$	107.4

The timing of revenue recognition, billings and cash collections results in accounts receivable, contract assets and contract liabilities. Accounts receivable represent amounts where the Company has an unconditional right to the consideration and therefore only the passage of time is required for the Company to receive consideration due from the customer. Both lease and management type contracts have customers and clients where amounts are billed as work progresses or in advance in accordance with agreed-upon contractual terms. Billing may occur subsequent to or prior to revenue recognition, resulting in contract assets and contract liabilities. The Company, on occasion, receives advances or deposits from customers and clients, on both lease and management type contracts, before revenue is recognized, resulting in the recognition of contract liabilities.

Contract assets and liabilities are reported on a contract-by-contract basis and are included in Notes and accounts receivable, net, and Accrued expenses, respectively, on the Condensed Consolidated Balance Sheets. See Note 1. Significant Accounting Policies and Practices for additional detail on the write-off of accounts receivable. There were no impairment charges recorded on contract assets and contract liabilities for the three and six months ended June 30, 2020 and 2019.

The following table provides information about accounts receivable, contract assets and contract liabilities with customers and clients as of June 30, 2020 (unaudited) and December 31, 2019:

(millions)	June 30, 2020			December 31, 2019
Accounts receivable	$	93.3		$	151.3
Contract asset		7.0			11.0
Contract liability		(11.3	)		(19.4	)

Changes in contract assets which include recognition of additional consideration due from the customer are offset by reclassifications of contract asset balances to accounts receivable when the Company obtains an unconditional right to consideration, thereby establishing an accounts receivable. The following table provides information about changes to contract asset balances during the six months ended June 30, 2020 and 2019:

	Six Months Ended
(millions) (unaudited)	June 30, 2020			June 30, 2019
Balance, beginning of period	$	11.0		$	11.4
Additional contract assets		7.0			11.8
Reclassification to accounts receivable		(11.0	)		(11.4	)
Balance, end of period	$	7.0		$	11.8

Changes in contract liabilities primarily include additional contract liabilities and reductions of contract liabilities when revenue is recognized. The following table provides information about changes to contract liability balances during the six months ended June 30, 2020 and 2019:

	Six Months Ended
(millions) (unaudited)	June 30, 2020			June 30, 2019
Balance, beginning of period	$	(19.4	)	$	(19.1	)
Additional contract liabilities		(11.3	)		(14.9	)
Recognition of revenue from contract liabilities		19.4			19.1
Balance, end of period	$	(11.3	)	$	(14.9	)

Cost of contracts, net, represents the cost of obtaining contractual rights associated with providing services for management type contracts. Incremental costs incurred to obtain service contracts are amortized on a straight line basis over the estimated life of the contracts, including anticipated renewals and terminations. This is consistent with the timing of when the Company satisfies the related performance obligations. Estimated lives are based on the contract life or anticipated lives of the contract.

Amortization expense related to cost of contracts not considered service concession arrangements is included within Depreciation and amortization in the Condensed Consolidated Statements of Income. Amortization expense of cost of contracts related to service concession arrangements within the scope of Topic 853 and certain management type contracts are recorded as a reduction of revenue and were not significant for the three and six months ended June 30, 2020 and 2019, respectively. Amortization expense related to cost of contracts for the three and six months ended June 30, 2020 and 2019 was as follows:

	Three Months Ended				Six Months Ended
(millions) (unaudited)	June 30, 2020		June 30, 2019		June 30, 2020		June 30, 2019
Amortization expense	$	0.3	$	0.3	$	0.7	$	0.6

As of June 30, 2020 and December 31, 2019, cost of contracts net of accumulated amortization included on the Condensed Consolidated Balance Sheets within Other noncurrent assets was $5.4 million and $4.3 million, respectively. No impairment charges were recorded for the three and six months ended June 30, 2020 and 2019, respectively.